Method for production of a mouldable mass and use thereof for production of low-emission floor coverings

ABSTRACT

A method for the production of moldable masses is provided. The method includes compounding a polyolefin having a density of less than about 0.918 g/cm 3  serial cross-linking agents. The moldable masses can be used the production of low-emission floor coverings with excellent material properties.

RELATED APPLICATION

This present application is a § 371 national phase application of PCTapplication serial no. PCT/EP02/09018, filed on Aug. 12, 2002, and whichclaims priority under 35 U.S.C. §119(b) to German application serial no.101 39 738.0-43, filed on Aug. 13, 2001. German application serial no.101 39 738.0-43 and PCT application serial no. PCT/EP02/09018 are herebyincorporated by reference in their entireties as if fully set forthherein.

TECHNICAL FIELD

The invention at hand relates to a method for the production oflow-emission floor coverings.

BACKGROUND

Elastomer coverings on rubber basis are part of high-performance floorcoverings due to their durability and multiple applicationpossibilities. However, the curing and processing additives or agents,respectively, are inclined to emit from the floor coverings in theirunchanged, or their chemically changed forms. WO 97/47802 and WO99/58602 have therefore described floor coverings, which essentially donot cause any annoying odor or health affecting emissions. Such floorcoverings are based on polyolefin with a density of <0.918 g/cm³ for thepolymer binder. In the course of further development for low-emissionfloor coverings, it has been shown that the processing methods in theproduction of such floor coverings may have a substantial influence ontheir material properties.

SUMMARY

The invention at hand relates to a method for the production of moldablemasses on the basis of polyolefin with a density of <0.918 g/cm³ bymeans of at least two delayed cross-linking reactions, as well as theuse of such masses for the production of low-emission floor coveringswith excellent material properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. FIG. 1 provides a schematic illustration of a device accordingto this invention in which one arrangement of the enclosure of theextruder is exemplified.

This task is solved by means of the embodiments characterized in theclaims. One method in particular for production of a moldable mass isprovided, which is comprised of the following steps:

(a) Compounding of a blend that contains at least one polyolefin with adensity of <0.918 g/cm³, for example 0.86 to 0.91 g/cm³, a first organicperoxide compound, such as 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexane(“DHBP”), with a decomposition temperature T1 of, for instance,approximately ≧160° C., and at a temperature of <T1, a firstco-cross-linking agent, which is essentially stable at a temperature of<T1.

(b) Adding of mineral oil, preferably paraffin mineral oil with as fewunsaturated proportions as possible, such as SUNPAR® 150, to the blendfrom step (a), preferably at a quantity of 2 to 25 weight-% based on theamount of the polyolefin, and heating of this blend to a temperature T2,such as approximately 180° C.; and

(c) Adding of at least a second organic peroxide compound, such as1,1-di-(5-butylperoxy)-3,3,5-trimethylcyclohexane, with a decompositiontemperature T3 and a second co-cross-linking agent, which is essentiallystable at a temperature of <T3 to the blend of step (b), and heating ofthe resulting blend to a temperature of ≧T3, such as to approximately≧185° C. while maintaining the moldable mass,

whereby T1<T2<T3.

The polyolefin used in step (a) can be a polyethylene of very lowdensity (“PE-VLD”), or a copolymer from ethylene with at least oneadditional olefin, such as propane, butane, or octane, and/or a blend ofat least two ethylene-copolymers, whereby as the main polymer, theethylene-copolymer has a copolymer (i) with a density of 0.88–0.91g/cm³, and for controlling rheology and elasticity, a copolymer (ii)with a density of 0.86–0.89 g/cm³, and an MFI of >3 (at 190° C.; 2.16kg). For example, the copolymers (i) and (ii) are copolymers of ethylenewith octane. The copolymers (i) and (ii), can be present, for instance,at a weight ratio of 4:1 to 3:2. Furthermore, as an additional componentin addition to polyolefin, at least one graft polymer may be present,preferably on the basis of an HD-polyethylene. In particular, the graftpolymer can be maleic acid anhydride grafted HD-polyethylene, wherebythe degree of grafting is preferably 1 to 5%. The proportion of thegraft polymer is, for example, 5 to 25 weight-% based on the totalweight of the polymer proportions used in step (a). Accordingly, theproportion of at least one polyolefin, which in addition to the graftpolymer forms the polymer proportion of the blend in step (a), can bebetween 75 to 95 weight percent, based on the total weight of thepolymer proportions.

The first organic peroxide compound used in step (a) is not onlycomprised of individual compounds, but can also be comprised of a blendof at least two like peroxide compounds, provided that both theindividual compounds and such a blend have a pre-determineddecomposition temperature of ≧T1. For example, the decompositiontemperature of the DHBP used in step (a) is ≧170° C. The first organicperoxide compound is present in the blend to be compounded; preferablyat an amount of 0.05 to 2.0 weight-% based on the amount of polyolefin.

The first co-cross-linking agent used in step (a), which is essentiallystable at a temperature of <T1, is preferably selected from a groupconsisting of di- and trimethacrylatene, such as1,4-butanedioldimethacrylate (“1,4-BDMA”), 1,3-butanediol-dimethacrylate(“1,3-BDMA”), triethyleneglycoidimethacrylate (“TEDMA”), andtrimethylolpropanetrimethacrylate (“TRIM”), and blends thereof. TheCo-cross-linking agent is present in the blend to be compoundedpreferably at an amount of 0.05 to 4.0 weight-% based on the amount ofpolyolefin.

The blend to be compounded in step (a) may further contain commonprocessing auxiliary agents, such as interior/exterior lubricants, suchas from the group of waxes, such as metal salts; static inhibitors, suchas GMS; antioxidants, such as phenol-inhibited amines, etc. Theseprocessing auxiliary agents are used in traditional quantities, such as1 to 5 weight-% based on the polymer proportions.

The mineral oil added in step (b) to the blend to be compounded in step(a) should preferably be low in aromatic compounds, i.e. have noaromatic residue or group, respectively, such as a phenyl group, whereby2 to 25 weight-% based on the amount of the polyolefin are added.

The second organic peroxide compound added in step (c) is not onlycomprised of individual compounds, but can also be comprised of a blendof at least two such peroxide compounds, provided that both theindividual compounds and the blend have a pre-determined decompositiontemperature of ≧T3. The second organic peroxide compound is preferablyadded at a quantity of 0.05 to 2.0 weight percent based on the amount ofpolyolefin.

The second co-cross-linking agent added in step (c), which isessentially stable at a temperature of <T3, may contain, for example,triallyl cyanurate (TAC) and/or triallyl isocyanurate (TAIC), wherebythe co-cross-linking agent is added at a quantity of 0.05 to 5 weight-%based on the amount of the polyolefin.

In a preferred embodiment of the method according to the invention, thesecond co-cross-linking agent has an accelerating effect on theperoxidic cross-linking reaction. Especially preferred aredimethacrylate as the first co-cross-linking agent, as opposed to, forexample, TRIM, because a larger amount of additive can be achieved at anequal MFI, which advantageously results in surface energy of floorcoverings on the basis of the mass according to the invention by meansof a higher content of polar groups.

In step (c) of the method according to the invention common fillers,such as silica flour, kaolin, talc, wood flour, dolomite,aluminumtrihydroxide, precipitated silica, barite, chalk, as well ascommon pigments can also be added.

The quantities of fillers and pigments used are within common ranges,and are, for example, up to 70% for fillers, and for example, up to 8%for pigments based on the total formulation.

The temperature T1 in step (a) of the method according to the inventionis preferably selected so that the polyolefin used can be plasticized inaddition to the compounding with the first organic peroxide compound andthe Co-cross-linking agent, but no decomposition of the first organicperoxide compound due to the temperature occurs. When using for exampleOHBP as the first organic peroxide compound, the temperature T1 ismaintained at ≦160° C., preferably between approximately 120 to 160° C.,i.e. below the decomposition temperature of DHBP. At this temperature,adequate plasticizing of the blend to be compounded can be achieved.

The temperature T2 in step (b) of the method according to the inventionis selected so that after adding the mineral oil, the cross-linkingreaction is activated between the first organic peroxide and theco-cross-linking agent. This “main reaction” of the blend plasticizedand compounded according to step (a) is performed using, for example,DHBP at approximately 180° C.

The temperature T3 in step (c) of the method according to the inventionis selected so that after adding the second organic peroxide compoundand the second co-cross-linking agent, the “final cross-linking” isensured, i.e. the first and second peroxide compounds used shouldpreferably be completely converted during the residence time in theextruder. When using, for example,1,1-DI-(t-butylperoxy)-3,3,5-trimethylcyclohexane as the second organicperoxide compound, the temperature T3 is ≧185° C.

The temperature direction of steps (a) to (c) of the method according tothe invention can be controlled or adjusted by means of extreme and/orinternal reaction enclosure temperature units, and/or by means offriction initiating worm elements with the use of twin worm extruders.The time for performing steps (a) to (c) of the method according to theinvention usually lasts 1 to 4 minutes. For example, with the use of atwin worm extruder, the residence time depends on the type of wormequipment and is selected so that in dependency of the throughput to beachieved, the blend remains in the enclosure for an accordingly longtime, preferably for approximately 1 to three minutes.

In a preferred embodiment of the method according to the invention,degassing of the mass achieved is performed after step (c), such asatmospheric ventilation followed by vacuum ventilation.

An additional subject of the invention at hand relates to the productionof floor coverings using the previously defined moldable mass. In oneembodiment, the method according to the invention is comprised ofproviding a carrier in the shape of webs, as well as the application ofthe previously defined moldable mass onto one side of the carrier. Anymaterial currently used in the floor covering sector on the basis ofnatural and/or synthetic woven fabric or knitted fabrics, textilematerial, as well as materials on the basis of non-woven materials ornon-woven fabrics, may be used. For example, jute fabrics, blendedfabrics made of natural fibers such as cotton and cellulose, fiber glassfabrics, fiber glass fabrics coated with bonding agents, blended fabricsmade of synthetics, fabrics made of core/compound glass fiber with, forexample, a core of polyester and a polyamide coating, may be used.

In another embodiment of the method according to the invention for theproduction of particularly homogenous floor coverings, the moldable masscreated, for example, in a twin worm extruder can be processed into foilby means of a flat die and calendar stack or a roller mill. This foilcan be further processed into any desired floor covering, for example,by means of sprinkling on a differently designed granulate, orcontinuously by means of a twin auma or twin press.

In another embodiment granulates yielded from the moldable mass, or themill feed thereof, can be fixed to a area-measured material by means ofsprinkling it on a liner in a Thermofix® system. Compression andsmoothing of the product web achieved in this way occurs in an auma. Thedirect production of a floor covering by means of stacking of mill feedor granulate is also possible in a twin auma or twin press. As far asthe production of homogenous floor coverings with directional structureis concerned, multi-colored granulates or blends of several monochromegranulates can be added into the groove of a roller mill/calendar.

An additional subject of the invention at hand is a floor covering,which can be quickly produced according to one of the previously definedmethods. Surprisingly it was shown in the floor covering according tothe invention that without a corona treatment an increase of surfaceenergy can be achieved, which, among other reasons, is a cause of theuse of the Co-cross-linking agents in steps (a) and (c) of the methodaccording to the invention. For example, by using 1,3-BDMA and/or1,4-BDMA as the first co-cross-linking agent in step (a) of the methodaccording to the invention, the proportion of the polar groups andthereby the surface energy can be selectively increased. Due to thehigher surface energy, the floor covering according to the invention hasa “direct gluability” as compared to traditional olefin floor coverings.Furthermore, a (“three-dimensional”) network is constructed by means ofthe delayed decomposition of the peroxides in steps (a) and (c) of themethod according to the invention and in the related cross-linkingreactions, which results in excellent material properties of the floorcovering.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures show the following:

FIG. 1 is a schematic illustration of a device for the production of thefloor covering according to the invention (also compare example 1). Thearrangement of the enclosure of the extruder is comprised of tenenclosure zones, whereby the compound blend according to step (a) isadded to the enclosure zone 1, the mineral oil according to step (b) isadded at the end of the enclosure zone 3, and the blend according tostep (c) is added in the enclosure zone 4 by means of a twin worm feedextruder (ZSB 40) at a temperature of ≦28° C. The rear ventilation islocated at the beginning of the enclosure zone 4, the atmosphericventilation (“A”) is located in the enclosure zone 6, and the vacuumventilation (“A”) is located in the enclosure zone 9. The respectiveenclosure temperature is stated in ° C. below each enclosure zone.

The invention at hand is explained in further detail by means of thefollowing examples.

EXAMPLE 1

A densely combing equi-directionally rotating twin worm extruder of thetype ZSK 40 from Coperion Werner+Pfleiderer with L/O=40 and D=40 is usedto perform the method according to the invention (compare FIG. 1). Thecompound blend (compare the following formulation for step (a)) isplasticized and homogenized within a 6D long feeder zone by means ofsuitable conveying and kneading elements. The temperature in this caseis approximately 180° C. After adding the mineral oil (SUNPAR 150®, 11.5weight-%) the temperature is increased by means of friction and shearrates of the worm elements, and initializes the peroxidic cross-linkingessentially between the first organic peroxide DHBP and theco-cross-linking agent 1,4-BDMA. The temperature is now approximately185° C. Subsequently, the blend according to step (c) is added in thefollowing formulation by means of a lateral extruder. Since thetemperature of the mass is higher than the decomposition temperature ofthe second organic peroxide compound, the final cross-linking is nowinitiated. The temperature in this case is approximately 195° C. Beforeexiting the extruder, a degassing by means of atmospheric ventilationfollowed by vacuum ventilation is performed in order to remove anyvolatile reaction products as well as any volatile educts so that theywill be unable to pollute the air in the future room.

Formulation for Example 1

Raw Materials Quantity [g] Proportion to total formulation Compoundblend, step (a) Affinity PL 1880 375.00  5.68% Affinity VP 8770 2,250.0034.10% Dow XU 60769.07 375.00  5.68% Processing Auxiliary 59.4  0.9%Agents (Additive mix) 1.4-BDMA 5.30 0.080% Trigonox 101-50 D-Pd 6.600.100% Mineral Oil Additive, step (b) SUNPAR 150 330.00  5.00% Fillerblend (lateral extruder), step (c) Filler 2,904.00 44.02% Trigonox 29-40B-Pd 21.10 0.320% Perkalink 301-50 4.25 0.064% Pigment blend 267  4.05%

The following lists the properties of the floor covering producedaccording to the invention with the previously mentioned mass:

1. Indentation Behavior according to EN 433 Remaining indentation after150 min. mm 0.01 Thickness before load mm 2.34 Penetration depth after150 min. mm 0.13 Index after 150 min. mm 5.6 Elasticity after 150 min. %92.3 2. Shore Hardness according to DIN 53 505 Shore A 96 Shore D 45 3.[Illegible] Behavior according to DIN 53 516 Raw density, EN 436 g/cm³1.335 Loss of volume mm³ 94.5Surface energy of the floor covering produced according to the inventionTesting Method

Determination of surface energy of the samples by means of contact anglemeasurement. Di-iodine methane (Busscher) and water (Busscher) were usedas the test liquids. The analysis is performed according to Owens,Wendt, Rabel & Kaelble.

Test Results

Surface energy Disperser Proportion Polar proportion Sample [mN/m][mN/m] [mN/m] Elastomer Tile 36.5 34.6 1.9

1. A method for the production of a moldable mass, comprising: (a)compounding, at a first temperature, a blend that contains at least onepolyolefin with a density of less than about 0.918 g/cm³, a firstorganic peroxide compound with a first decomposition temperature, and afirst co-cross-linking agent, wherein the first co-cross-linking agentis substantially stable at temperatures less than the firstdecomposition temperature; (b) adding of mineral oil to the compoundedblend of step (a), and heating of this blend to a second temperature;and (c) adding of at least one second organic peroxide compound with asecond decomposition temperature, and a second co-cross-linking agent,which is substantially stable at temperatures less than the seconddecomposition temperature to the blend of step (b), and heating of theresulting blend to a temperature of above the second decompositiontemperature while yielding the moldable mass, wherein the firsttemperature is less than the first decomposition temperature, the firstdecomposition temperature is less than the second temperature and thesecond temperature is less than the second decomposition temperature. 2.The method according to claim 1, wherein the polyolefin is polyethyleneof very low density (PE-VLD), a copolymer of ethylene with at least oneadditional olefin, or a blend of at least two ethylene copolymer.
 3. Themethod according to claim 1, wherein the polyolefin has a density ofabout 0.86 to about 0.91 g/cm³.
 4. The method according to claim 1,wherein the first organic peroxide compound is2,5-dimethyl-2,5-di-(t-butylperoxy)-hexane (DHBP).
 5. The methodaccording to claim 1, wherein the first organic peroxide compound ispresent at a quantity of about 0.05 to about 2.0 weight-percent based onthe amount of the polyolefin.
 6. The method according to claim 1,wherein the first co-cross-linking agent contains a compound selectedfrom dimethacrylates and trimethacrylates.
 7. The method according toclaim 6, wherein the dimethacrylates and trimethylacrylates are selectedfrom the group 1,4-butanedioldimethacrylate (1,4-BDMA),1,3-butanediol-dimethacrylate (1,3-BDMA),triethyleneglycoidimethacrylate (TEDMA, andtrimethylolpropanetrimethacrylate (TRIM).
 8. The method according toclaim 1, wherein the first co-cross-linking agent is present at aquantity of about 0.05 to about 4.0 weight-percent based on the amountof the polyolefin.
 9. The method according to claim 1, wherein the blendin step (a) contains a processing auxiliary agent.
 10. The methodaccording to claim 1, wherein the mineral oil is added at a quantity ofabout 2 to about 25 weight-percent based on the amount of thepolyolefin.
 11. The method according to claim 1, wherein the secondperoxide compound is 1,1-di-(t-butylperoxy)-2,3,5-trimethylcyclohexane.12. The method according to claim 1, wherein the second peroxidecompound is added at a quantity of about 0.05 to about 2.0weight-percent based on the amount of the polyolefin.
 13. The methodaccording to claim 1, wherein the second co-cross-linking agent containsa compound selected from triallyl cyanurate (TAC) and triallylisocyanurate (TAIC).
 14. The method according to claim 1, wherein thesecond co-cross-linking agent is added at a quantity of about 0.05 toabout 5.0 weight-percent based on the amount of the polyolefin.
 15. Themethod according to claim 1, wherein step (c) further comprises adding afiller.
 16. The method according to claim 1, in which the firstdecomposition temperature is approximately less than or equal to 160°C., the second temperature is approximately 180° C., and the seconddecomposition temperature is approximately less than or equal to 185° C.17. The method according to claim 1, in which the time for performingsteps (a) to (c) is approximately 1 to 3 minutes.
 18. The methodaccording to claim 1, in which degassing is performed after step (c).19. The method according to claim 1, further comprises forming themolded mass into a floorcovering.
 20. The method of claim 2, wherein theblend further comprises a graft polymer.
 21. The method of claim 1,wherein step (c) further comprises adding a pigment.